The role of natural killer (NK) cells in reproductive failure has been investigated extensively, but the topic remains controversial and poorly understood. NK cells are known to play an important protective role in cancer and infection, but the implications of high NK cell levels have not been studied with respect to these diseases. This study aimed to identify any differences in reproductive outcomes as well as general health and disease between women with high and normal NK cell parameters.

Polycystic ovary syndrome (PCOS) is associated with an increased risk of miscarriage, occurring in 30% of pregnancies. Although the mechanism is unclear, several interrelated factors appear to increase the risk of spontaneous miscarriages, including higher luteinising hormone levels, obesity, hyperandrogenisation, insulin resistance and infertility treatments.

Few topics in recent reproductive medicine have been the subject of as much controversy, media attention and passionate debate as natural killer (NK) cells and their role in reproductive failure. The question of whether elevated NK cell levels are a cause of infertility and pregnancy loss, and whether they provide a potential target for therapy to improve reproductive outcomes, lacks a definitive answer. It is clear, however, that a significant number of women with reproductive failure have abnormal NK cell parameters reflecting high immunological activity.

Amongst all the debate, the wider implications of NK cell overactivity – and attempts to suppress it – have not yet been considered. The literature suggests that although elevated NK cell activity may not be conducive to reproduction, it could in fact be beneficial in other areas of health and disease such as cancer and infection. Further research is needed to determine whether this hypothesis holds true in women with NK cell-related reproductive failure.

Luteinizing hormone (LH) supplementation in IVF cycles has been a debated topic for many years [1-4]. Whilst follicle stimulating hormone (FSH) alone achieves adequate ovarian stimulation it is still possible that, in some circumstances, better results could be achieved with a combined approach.

Natural killer cell testing is currently practised widely, and there are studies indicating potential benefit in terms of targeting women with repeated reproductive failure for immune therapy. This may be a better approach than empirical immune therapy without any investigation. More and better studies are needed before such an approach can be fully endorsed.

In this retrospective study, between 2008 and 2013, couples with a history of recurrent miscarriage (≥3 first trimester miscarriages) were investigated comprehensively for known causes (karyotype, uterine, antiphospholipid syndrome, thrombophilia) and also by semen analysis, including DNA fragmentation [sperm chromatin structure analysis (SCSA)]. Statistical analysis was performed on SPSS software with significance taken as P < 0.05.

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About Dr Gavin Sacks

Gavin completed his medical training at both Cambridge and Oxford Universities, including a degree in experimental psychology. He then trained further in clinical medicine in Leeds, Glasgow, London and Sydney.

At the same time, scientists were making ground-breaking advances in IVF technology. Gavin wanted to be a part of this medical revolution that was bringing real hope to infertile couples and is now one of Australia's leading IVF specialists.